1. Field of the Invention
The present invention relates to an improvement in a magnetic disk apparatus for reading and writing information to a magnetic disk, used as a storage apparatus for a computer apparatus.
2. Description of the Related Art
FIGS. 10A and 10B are drawings showing a magnetic disk apparatus; a cross sectional view (FIG. 10A) and a view from above (FIG. 10B) are shown. Also, FIG. 11 is a view from above of the magnetic disk apparatus with the cover 8 in FIGS. 10A and 10b removed. In FIG. 10A, a DC motor 2 is mounted on the base 1. At least one magnetic disk 3 is mounted on the DC motor 2 so as to be capable of rotating about the center of the DC motor 2. In FIG. 10A, five magnetic disks 3, for example, with spacers 4 fitted between them, are pressed together by a screw fastening using a disk clamp 5, and are mounted on the DC motor 2. Also, as shown in FIG. 11, an actuator arm 6 is disposed with a head 7 for reading from and writing to the magnetic disk 3, the aforementioned head being mounted on the end of the aforementioned arm.
The cover 8 shown in FIGS. 10A and 10B encloses the abovementioned constituent elements. The cover 8 comprises a recessed portion; a damping plate 9 is attached to the outer surface thereof using an element made of a viscoelastic material. In this way, noise generated by the magnetic disk apparatus can be suppressed to a certain extent.
The performance of such magnetic disk apparatuses has improved markedly in recent years, but further noise reductions are required.
Also, higher density storage capacities and increased access speeds for the magnetic disk apparatuses are required. One method of increasing the density of storage capacity may be to reduce the track pitch on the magnetic disk, for example. One method of increasing access speed may be to raise the speed of rotation of the magnetic disk.
However, simply narrowing the track pitch on the magnetic disk, or simply raising the speed of rotation of the magnetic disk, results in decreases in the signal to noise (S/N) ratio of the positioning error signal, which indicates the displacement of the head in relation to the track. One cause of this is known to be the disk resonance due to disk rotation. The position detection precision of the heads drops due to the decrease in the SIN ratio of the positioning error signal so that the probability of operating errors such as reading errors becomes high. Consequently, means for suppressing magnetic disk resonance are being sought.
Furthermore, a magnetic disk in a magnetic disk apparatus is attached with a disk clamp as discussed above. However, there is a risk that the position of the magnetic disk will be displaced within the magnetic disk apparatus by a shock or the like (the displacement is in units of microns). Major problems such as errors in accessing the magnetic disk occur as a result of the displacement of the position of the magnetic disk. Improvement to the shock-resistance performance is also required for this reason.
It is an object of the present invention to provide a magnetic disk apparatus with various improvements for noise reduction, suppression of magnetic disk resonance, and improvements in shock-resistance performance.
In order to achieve the abovementioned object, a first invention relating to the present invention provides a magnetic disk apparatus comprising a motor mounted on a base; at least one magnetic disk mounted on the motor; an arm having at least one head for reading and writing information to the magnetic disk and turning so as to traverse the surface of the magnetic disk; and a cover for enclosing the motor, the magnetic disk, and the arm on the base; wherein the inner surface of the cover is opposite to the magnetic disk surface, the cover has a first recessed portion in a first region corresponding to the magnetic disk surface that is not traversed by the arm and a second recessed portion in a second region corresponding to the magnetic disk surface that is traversed by the arm, and the space between the inner surface of the first region and the magnetic disk surface becomes narrower than the space between the inner surface of the second region and the magnetic disk surface by making the depth of the first recessed portion greater than the depth of the second recessed portion.
In this way, with the first invention, the recessed portion of the cover of the magnetic disk apparatus has a two-level structure, and the space between the inner surface of the recessed portion corresponding to the region of the magnetic disk surface that is not traversed by the actuator arm and the surface of the magnetic disk is made as small as possible. The flow of air generated in that space by the rotation of the magnetic disk is thereby suppressed, and as a result, the resonance of the magnetic disk is suppressed.
The magnetic disk apparatus relating to the first invention preferably comprises a first damping plate mounted on the first recessed portion, and a second damping plate mounted on the second recessed portion and above the first damping plate. In this way, the noise level is further suppressed by having two layers of damping plates applied to the outer surface of the cover. In the magnetic disk apparatus relating to the first invention, the outer surface of the cover, whereon the first damping plate and second damping plate are mounted, is preferably essentially flat. It thereby becomes easy to attach a name plate label or the like on the upper surface of the cover.
In order to achieve the abovementioned object, the second invention relating to the present invention provides a magnetic disk apparatus comprising a motor mounted on a base; a plurality of magnetic disks mounted on the motor; spacers forming a prescribed interval between each of the magnetic disks; and heads for reading and writing information to the magnetic disks; wherein a groove element is formed on that part of the surface of the spacer which makes contact with the magnetic disk; and that groove element is made of a viscoelastic material.
For example, the spacer is ring-shaped and includes a groove element along the circumference of the surface that makes contact with the magnetic disk; a viscoelastic material element is preferably mounted in the groove element. Also, the spacer may be ring-shaped and include a groove element extending in a radial direction on the surface which makes contact with the magnetic disk; a viscoelastic material element is preferably mounted in the groove element.
In order to achieve the abovementioned object, the third invention relating to the present invention provides a magnetic disk apparatus comprising a motor mounted on a base; at least one magnetic disk to which information is written and read by heads; and a clamp for pressing and mounting the magnetic disk on the supporting portion of the motor, wherein at least part of the surface of the clamp in contact with the magnetic disk is made of a viscoelastic material.
In order to achieve the abovementioned object, the fourth invention relating to the present invention provides a magnetic disk apparatus comprising a motor mounted on a base; at least one magnetic disk to which information is written and read by heads; and a clamp for pressing and mounting the magnetic disk on the supporting portion of the motor, wherein at least part of the surface of the supporting portion of the motor in contact with the magnetic disk is made of a viscoelastic material.
In order to achieve the abovementioned object, the fifth invention relating to the present invention provides a magnetic disk apparatus comprising a motor mounted on a base; a plurality of magnetic disks mounted on the motor; ring-shaped spacers forming a prescribed interval between each of the magnetic disks; O-rings disposed around the spacers and in contact with the magnetic disks; and heads for reading and writing information to the magnetic disks.
In this way, with the second, third, fourth, and fifth inventions, viscoelastic material elements, O-rings, or the like are placed in contact with the magnetic disks. These suppress the resonance of the magnetic disks.
In order to achieve the abovementioned object, the sixth invention relating to the present invention provides a magnetic disk apparatus comprising at least one magnetic disk; a motor for rotating the magnetic disk; a disk-shaped clamp for mounting the magnetic disk on the motor by screw fastening; a C-shaped balancer for adjusting the rotary balance of the magnetic disk and mounted on the outer surrounding portion of the clamp; and a head for reading and writing information to the magnetic disk.
With the sixth invention, it becomes unnecessary to create different levels on the clamp surface in order to mount on the clamp a balance-adjusting weight, which is conventionally used. Consequently, the rigidity of the clamp is increased because the clamp can be made thicker and, as a result, the shock-resistance performance of the magnetic disk apparatus can be improved.